Chucking system for modulating shapes of substrates

ABSTRACT

The present invention is directed to a chucking system to modulate substrates so as to properly shape and position the same with respect to a wafer upon which a pattern is to be formed with the substrate.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a continuation application of U.S. patentapplication Ser. No. 10/293,224, filed Nov. 13, 2002, having Byung-JinChoi, Ronald D. Voisin, Sidlgata V. Sreenivasan, Michael P. C. Watts,Daniel A. Babbs, Mario J. Meissl, Hillman L. Bailey, and Norman E.Schumaker listed as inventors, which is incorporated herein by referencein its entirety.

FIELD OF THE INVENTION

The field of invention relates generally to lithography systems. Moreparticularly, the present invention is directed to reducing undesirablepattern variations during imprint lithography processes.

Micro-fabrication involves the fabrication of very small structures,e.g., having features on the order of micro-meters or smaller. One areain which micro-fabrication has had a sizeable impact is in theprocessing of integrated circuits. As the semiconductor processingindustry continues to strive for larger production yields whileincreasing the circuits per unit area formed on a substrate,micro-fabrication becomes increasingly important. Micro-fabricationprovides greater process control while allowing increased reduction ofthe minimum feature dimension of the structures formed. Other areas ofdevelopment in which micro-fabrication have been employed includebiotechnology, optical technology, mechanical systems and the like.

An exemplary micro-fabrication technique is shown in U.S. Pat. No.6,334,960 to Willson et al. Willson et al. disclose a method of forminga relief image in a structure. The method includes providing a substratehaving a transfer layer. The transfer layer is covered with apolymerizable fluid composition. A mold makes mechanical contact withthe polymerizable fluid. The mold includes a relief structure, and thepolymerizable fluid composition fills the relief structure. Thepolymerizable fluid composition is then subjected to conditions tosolidify and to polymerize the same, forming a solidified polymericmaterial on the transfer layer that contains a relief structurecomplimentary to that of the mold. The mold is then separated from thesolid polymeric material such that a replica of the relief structure inthe mold is formed in the solidified polymeric material. The transferlayer and the solidified polymeric material are subjected to anenvironment to selectively etch the transfer layer relative to thesolidified polymeric material such that a relief image is formed in thetransfer layer. The time required and the minimum feature dimensionprovided by this technique is dependent upon, inter alia, thecomposition of the polymerizable material.

U.S. Pat. No. 5,772,905 to Chou discloses a lithographic method andapparatus for creating ultra-fine (sub-36 nm) patterns in a thin filmcoated on a substrate in which a mold having at least one protrudingfeature is pressed into a thin film carried on a substrate. Theprotruding feature in the mold creates a recess in the thin film. Themold is removed from the film. The thin film then is processed such thatthe thin film in the recess is removed exposing the underlyingsubstrate. Thus, patterns in the mold are replaced in the thin film,completing the lithography. The patterns in the thin film will be, insubsequent processes, reproduced in the substrate or in another materialwhich is added onto the substrate.

Yet another imprint lithography technique is disclosed by Chou et al. inUltrafast and Direct Imprint of Nanostructures in Silicon, Nature, Col.417, pp. 835–837, June 2002, which is referred to as a laser assisteddirect imprinting (LADI) process. In this process a region of asubstrate is made flowable, e.g., liquefied, by heating the region withthe laser. After the region has reached a desired viscosity, a mold,having a pattern thereon, is placed in contact with the region. Theflowable region conforms to the profile of the pattern and is thencooled, solidifying the pattern into the substrate. An importantconsideration when forming patterns in this manner is to maintaincontrol of the mold. In this fashion, undesirable variations in thepattern resulting from, inter alia, undesired deformation of the moldmay be avoided. For example, in-plane distortion can cause line widthvariations, as well as pattern placement errors. Out-of-plane distortioncan cause loss of focus in optical lithography, resulting in thicknessvariations of the underlying residual layers. This may make difficultboth line width control and etch transfer.

It is desired, therefore, to provide improved techniques for holding themold so as to properly position the same with respect to the substrateupon which a pattern is to be formed.

SUMMARY OF THE INVENTION

The present invention is directed to a chucking system to modulatesubstrates so as to properly shape a mold and position the same withrespect to a wafer upon which a pattern is formed using the mold. Thechucking system includes a chuck body having first and second opposedsides with a side surface extending therebetween. The first sideincludes first and second spaced-apart recesses defining first andsecond spaced-apart support regions. The first support region cincturesthe second support region and the first and second recesses. The secondsupport region cinctures the second recess with a portion of the body insuperimposition with the second recess being transparent to radiationhaving a predetermined wavelength. The portion extends from the secondside and terminates proximate to the second recess. The second side andthe side surface define exterior surfaces. The body includes first andsecond throughways extending through the body, placing the first andsecond recesses, respectively, in fluid communication with one of theexterior surfaces.

In another embodiment, a pressure control system is included. The firstthroughway places the first recess in fluid communication with thepressure control system and the second throughway places the pressurecontrol system in fluid communication with the second recess. Whenmounted to the chuck body, the substrate rests against the first andsecond support regions, covering the first and second recesses. Thefirst recess and the portion of the substrate in superimpositiontherewith define a first chamber and the second recess and the portionof the substrate in superimposition therewith defines a second chamber.The pressure control system operates to control a pressure in the firstand second chambers. Specifically, the pressure is established in thefirst chamber to maintain the position of the substrate with the chuckbody. The pressure in the second chamber may differ from the pressure inthe first chamber to, inter alia, reduce distortions in the substratethat occur during imprinting. These and other embodiments of the presentinvention are discussed more fully below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a lithographic system in accordance withthe present invention;

FIG. 2 is a simplified elevation view of a lithographic system shown inFIG. 1;

FIG. 3 is a simplified representation of material from which animprinting layer, shown in FIG. 2, is comprised before being polymerizedand cross-linked;

FIG. 4 is a simplified representation of cross-linked polymer materialinto which the material shown in FIG. 3 is transformed after beingsubjected to radiation;

FIG. 5 is a simplified elevation view of a mold spaced-apart from theimprinting layer, shown in FIG. 1, after patterning of the imprintinglayer;

FIG. 6 is a simplified elevation view of an additional imprinting layerpositioned atop of the substrate, shown in FIG. 5, after the pattern inthe first imprinting layer is transferred therein;

FIG. 7 is a detailed perspective view of a print head shown in FIG. 1;

FIG. 8 is a cross-sectional view of a chucking system in accordance withthe present invention;

FIG. 9 is an exploded view of an imprint head shown in FIG. 7;

FIG. 10 is a bottom-up plan view of a chuck body shown in FIG. 8;

FIG. 11 is a top down view of a wafer, shown in FIGS. 2, 5 and 6 uponwhich imprinting layers are disposed;

FIG. 12 is a detailed view of FIG. 11 showing the position of the moldin one of the imprint regions;

FIG. 13 is a bottom-up plan view of the chuck body shown in FIG. 8 inaccordance with an alternate embodiment;

FIG. 14 is a cross-sectional view of a chuck body shown in FIG. 8 inaccordance with a second alternate embodiment;

FIG. 15 is a flow diagram showing a method of reducing distortions inpatterns formed using imprint lithography techniques in accordance withthe present invention; and

FIG. 16 is a flow diagram showing a method of reducing distortions inpatterns formed using imprint lithography techniques in accordance withan alternate embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 depicts a lithographic system 10 in accordance with oneembodiment of the present invention that includes a pair of spaced-apartbridge supports 12 having a bridge 14 and a stage support 16 extendingtherebetween. Bridge 14 and stage support 16 are spaced-apart. Coupledto bridge 14 is an imprint head 18, which extends from bridge 14 towardstage support 16. Disposed upon stage support 16 to face imprint head 18is a motion stage 20. Motion stage 20 is configured to move with respectto stage support 16 along X- and Y-axes. A radiation source 22 iscoupled to system 10 to impinge actinic radiation upon motion stage 20.As shown, radiation source 22 is coupled to bridge 14 and includes apower generator 23 connected to radiation source 22.

Referring to both FIGS. 1 and 2, connected to imprint head 18 is asubstrate 26 having a mold 28 thereon. Mold 28 includes a plurality offeatures defined by a plurality of spaced-apart recessions 28 a andprotrusions 28 b. The plurality of features defines an original patternthat is to be transferred into a wafer 30 positioned on motion stage 20.To that end, imprint head 18 is adapted to move along the Z-axis and tovary a distance “d” between mold 28 and wafer 30. In this manner, thefeatures on mold 28 may be imprinted into a flowable region of wafer 30,discussed more fully below. Radiation source 22 is located so that mold28 is positioned between radiation source 22 and wafer 30. As a result,mold 28 is fabricated from material that allows it to be substantiallytransparent to the radiation produced by radiation source 22.

Referring to both FIGS. 2 and 3, a flowable region, such as animprinting layer 34, is disposed on a portion of surface 32 thatpresents a substantially planar profile. Flowable region may be formedusing any known technique such as a hot embossing process disclosed inU.S. Pat. No. 5,772,905, which is incorporated by reference in itsentirety herein, or a laser assisted direct imprinting (LADI) process ofthe type described by Chou et al. in Ultrafast and Direct Imprint ofNanostructures in Silicon, Nature, Col. 417, pp. 835–837, June 2002. Inthe present embodiment, however, the flowable region consists ofimprinting layer 34 being deposited as a plurality of spaced-apartdiscrete beads 36 of material 36 a on wafer 30, discussed more fullybelow. imprinting layer 34 is formed from a material 36 a that may beselectively polymerized and cross-linked to record the original patterntherein, defining a recorded pattern. Material 36 a is shown in FIG. 4as being cross-linked at points 36 b, forming cross-linked polymermaterial 36 c.

Referring to FIGS. 2, 3 and 5, the pattern recorded in imprinting layer34 is produced, in part, by mechanical contact with mold 28. To thatend, imprint head 18 reduces the distance “d” to allow imprinting layer34 to come into mechanical contact with mold 28, spreading beads 36 soas to form imprinting layer 34 with a contiguous formation of material36 a over surface 32. In one embodiment, distance “d” is reduced toallow sub-portions 34 a of imprinting layer 34 to ingress into and tofill recessions 28 a.

To facilitate filling of recessions 28 a, material 36 a is provided withthe requisite properties to completely fill recessions 28 a whilecovering surface 32 with a contiguous formation of material 36 a. In thepresent embodiment, sub-portions 34 b of imprinting layer 34 insuperimposition with protrusions 28 b remain after the desired, usuallyminimum distance “d”, has been reached, leaving sub-portions 34 a with athickness t₁, and sub-portions 34 b with a thickness, t₂. Thicknesses“t₁” and “t₂” may be any thickness desired, dependent upon theapplication. Typically, t₁ is selected so as to be no greater than twicethe width u of sub-portions 34 a, i.e., t₁≦2u, shown more clearly inFIG. 5.

Referring to FIGS. 2, 3 and 4, after a desired distance “d” has beenreached, radiation source 22 produces actinic radiation that polymerizesand cross-links material 36 a, forming cross-linked polymer material 36c. As a result, the composition of imprinting layer 34 transforms frommaterial 36 a to material 36 c, which is a solid. Specifically, material36 c is solidified to provide side 34 c of imprinting layer 34 with ashape conforming to a shape of a surface 28 c of mold 28, shown moreclearly in FIG. 5. After imprinting layer 34 is transformed to consistof material 36 c, shown in FIG. 4, imprint head 18, shown in FIG. 2, ismoved to increase distance “d” so that mold 28 and imprinting layer 34are spaced-apart.

Referring to FIG. 5, additional processing may be employed to completethe patterning of wafer 30. For example, wafer 30 and imprinting layer34 may be etched to transfer the pattern of imprinting layer 34 intowafer 30, providing a patterned surface 32 a, shown in FIG. 6. Tofacilitate etching, the material from which imprinting layer 34 isformed may be varied to define a relative etch rate with respect towafer 30, as desired. The relative etch rate of imprinting layer 34 towafer 30 may be in a range of about 1.5:1 to about 100:1. Alternatively,or in addition to, imprinting layer 34 may be provided with an etchdifferential with respect to photo-resist material (not shown)selectively disposed thereon. The photo-resist material (not shown) maybe provided to further pattern imprinting layer 34, using knowntechniques. Any etch process may be employed, dependent upon the etchrate desired and the underlying constituents that form wafer 30 andimprinting layer 34. Exemplary etch processes may include plasmaetching, reactive ion etching, chemical wet etching and the like.

Referring to both FIGS. 1 and 2, an exemplary radiation source 22 mayproduce ultraviolet radiation. Other radiation sources may be employed,such as thermal, electromagnetic and the like. The selection ofradiation employed to initiate the polymerization of the material inimprinting layer 34 is known to one skilled in the art and typicallydepends on the specific application which is desired. Furthermore, theplurality of features on mold 28 are shown as recessions 28 a extendingalong a direction parallel to protrusions 28 b that provide a crosssection of mold 28 with a shape of a battlement. However, recessions 28a and protrusions 28 b may correspond to virtually any feature requiredto create an integrated circuit and may be as small as a few tenths ofnanometers. As a result, it may be desired to manufacture components ofsystem 10 from materials that are thermally stable, e.g., have a thermalexpansion coefficient of less than about 10 ppm/degree centigrade atabout room temperature (e.g. 25 degrees Centigrade). In someembodiments, the material of construction may have a thermal expansioncoefficient of less than about 10 ppm/degree Centigrade, or less than 1ppm/degree Centigrade. To that end, bridge supports 12, bridge 14,and/or stage support 16 may be fabricated from one or more of thefollowing materials: silicon carbide, iron alloys available under thetrade name INVAR®, or name SUPER INVAR™, ceramics, including, but notlimited to, ZERODUR® ceramic. Additionally table 24 may be constructedto isolate the remaining components of system 10 from vibrations in thesurrounding environment. An exemplary table 24 is available from NewportCorporation of Irvine, Calif.

Referring to FIGS. 7 and 8, substrate 26, upon which mold 28 is present,is coupled to imprint head housing 18 a via a chucking system 40 thatincludes chuck body 42. Specifically, a calibration system 18 b iscoupled to imprint head housing 18 a, and chuck body 42 couplessubstrate 26 to calibration system 18 b vis-à-vis a flexure system 18 c.Calibration system 18 b facilitates proper orientation alignment betweensubstrate 26 and wafer 30, shown in FIG. 5, thereby achieving asubstantially uniform gap distance, “d”, therebetween.

Referring to both FIGS. 7 and 9, calibration system 18 b includes aplurality of actuators 19 a, 19 b and 19 c and a base plate 19 d.Specifically, actuators 19 a, 19 b and 19 c are connected betweenhousing 18 a and base plate 19 d. Flexure system 18 c includes flexuresprings 21 a and flexure ring 21 b. Flexure ring 21 b is coupled betweenbase plate 19 d and flexure springs 21 a. Motion of actuators 19 a, 19 band 19 c orientates flexure ring 21 b to allow for a coarse calibrationof flexure springs 21 a and, therefore, chuck body 42 and substrate 26.Actuators 19 a, 19 b and 19 c also facilitate translation of flexurering 21 b to the Z-axis. Flexure springs 21 a include a plurality oflinear springs that facilitate gimbal-like motion in the X-Y plane sothat proper orientation alignment may be achieved between wafer 30 andsubstrate 26, shown in FIG. 2.

Referring to FIGS. 8 and 10, chuck body 42 is adapted to retainsubstrate 26 upon which mold 28 is attached employing vacuum techniques.To that end, chuck body 42 includes first 46 and second 48 opposedsides. A side, or edge, surface 50 extends between first side 46 andsecond side 48. First side 46 includes a first recess 52 and a secondrecess 54, spaced-apart from first recess 52, defining first 58 andsecond 60 spaced-apart support regions. First support region 58cinctures second support region 60 and the first 52 and second 54recesses. Second support region 60 cinctures second recess 54. A portion62 of chuck body 42 in superimposition with second recess 54 istransparent to radiation having a predetermined wavelength, such as thewavelength of the actinic radiation mentioned above. To that end,portion 62 is made from a thin layer of transparent material, such asglass. However, the material from which portion 62 is made may dependupon the wavelength of radiation produced by radiation source 22, shownin FIG. 2. Portion 62 extends from second side 48 and terminatesproximate to second recess 54 and should define an area at least aslarge as an area of mold 28 so that mold 28 is in superimpositiontherewith. Formed in chuck body 42 are one or more throughways, shown as64 and 66. One of the throughways, such as throughway 64, places firstrecess 52 in fluid communication with side surface 50. The remainingthroughway, such as throughway 66, places second recess 54 in fluidcommunication with side surface 50.

It should be understood that throughway 64 may extend between secondside 48 and first recess 52 also. Similarly, throughway 66 may extendbetween second side 48 and second recess 54. What is desired is thatthroughways 64 and 66 facilitate placing recesses 52 and 54,respectively, in fluid communication with a pressure control system,such a pump system 70.

Pump system 70 may include one or more pumps to control the pressureproximate to recesses 52 and 54, independently of one another.Specifically, when mounted to chuck body 42, substrate 26 rests againstfirst 58 and second 60 support regions, covering first 52 and second 54recesses. First recess 52 and a portion 44 a of substrate 26 insuperimposition therewith define a first chamber 52 a. Second recess 54and a portion 44 b of substrate 26 in superimposition therewith define asecond chamber 54 a. Pump system 70 operates to control a pressure infirst 52 a and second 54 a chambers. Specifically, the pressure isestablished in first chamber 52 a to maintain the position of thesubstrate 26 with the chuck body 42 and reduce, if not avoid, separationof substrate 26 from chuck body 42 under force of gravity. The pressurein the second chamber 54 a may differ from the pressure in the firstchamber 52 a to, inter alia, reduce distortions in the substrate 26 thatoccur during imprinting, by modulating a shape of substrate 26. Forexample, pump system 70 may apply a positive pressure in chamber 54 a tocompensate for any upward force R that occurs as a result on imprintinglayer 34 contacting mold 28. In this manner, produced is a pressuredifferential between differing regions of side 46 so that bowing ofsubstrate 26 and, therefore, mold 28 under force R is attenuated, if notavoided.

Coupled to substrate 26 is a means to compress the same in X- andY-directions, with the understanding that the Y-direction is into theplane of FIG. 8. In the present example the means to compress includes afluid-tight bladder 72 surrounding substrate 26. However, any device maybe employed to that end, for example, a vice. Bladder 72 is in fluidcommunication with pump system 70 to control the fluid pressure inbladder 72. In this manner, bladder 72 may be used to apply a force tosubstrate 26 to vary the dimensions of the same and to reducedistortions in the pattern recorded into imprinting layer 34, shown inFIG. 2.

Specifically, distortions in the pattern recorded into imprinting layer34 may arise from, inter alia, dimensional variations of imprintinglayer 34 and wafer 30. These dimensional variations, which may be due inpart to thermal fluctuations, as well as, inaccuracies in previousprocessing steps that produce what is commonly referred to asmagnification/run-out errors. The magnification/run-out errors occurwhen a region of wafer 30 in which the original pattern is to berecorded exceeds the area of the original pattern. Additionally,magnification/run-out errors may occur when the region of wafer 30, inwhich the original pattern is to be recorded, has an area smaller thanthe original pattern. The deleterious effects of magnification/run-outerrors are exacerbated when forming multiple layers of imprintedpatterns, shown as imprinting layer 124 in superimposition withpatterned surface 32 a, shown in FIG. 6. Proper alignment between twosuperimposed patterns is difficult in the face of magnification/run-outerrors in both single-step full wafer imprinting and step-and-repeatimprinting processes.

Referring to FIGS. 11 and 12, a step-and-repeat process includesdefining a plurality of regions, shown as a-l, on wafer 30 in which theoriginal pattern on mold 28 will be recorded. The original pattern onmold 28 may be coextensive with the entire surface of mold 28, or simplylocated to a sub-portion thereof. The present invention will bediscussed with respect to the original pattern being coextensive withthe surface of mold 28 that faces wafer 30. Proper execution of astep-and-repeat process may include proper alignment of mold 28 witheach of regions a-l. To that end, mold 28 includes alignment marks 114a, shown as a “+” sign. One or more of regions a-l includes fiducialmarks 110 a. By ensuring that alignment marks 114 a are properly alignedwith fiducial marks 110 a, proper alignment of mold 28 with one ofregions a-l in superimposition therewith is ensured. To that end,machine vision devices (not shown) may be employed to sense the relativealignment between alignment marks 114 a and fiducial marks 110 a. In thepresent example, proper alignment is indicated upon alignment marks 114a being in superimposition with fiducial marks 110 a. With theintroduction of magnification/run-out errors, proper alignment becomesvery difficult.

However, in accordance with one embodiment of the present invention,magnification/run-out errors are reduced, if not avoided, by creatingrelative dimensional variations between mold 28 and wafer 30.Specifically, the temperature of wafer 30 is varied so that one ofregions a-l defines an area that is slightly less than an area of theoriginal pattern on mold 28. Thereafter, the final compensation formagnification/run-out errors is achieved by subjecting substrate 26,shown in FIG. 8, to mechanical compression forces using bladder 72,which are in turn transferred to mold 28 shown by arrows F₁ and F₂,orientated transversely to one another, shown in FIG. 12. In thismanner, the area of the original pattern is made coextensive with thearea of the region a-l in superimposition therewith.

Referring to both FIGS. 5 and 8, subjecting substrate 26 to compressiveforces, however, modulates the shape of the same through bending action.Bending of substrate 26 may also introduce distortions in the patternimprinted into imprinting layer 34. The pattern distortions attributableto bending of substrate 26 may be reduced, if not prevented, bypositioning bladder 72 so that the bending of substrate 26 is controlledto occur in a desired direction. In the present example, bladder 72 ispositioned to compress substrate 26 so as to bow in a direction parallelto, and opposite of, force R. By controlling the bending of substrate 26in this manner, chucking system 40 may be employed to counter thebending force, B, so as to establish mold 28 to be a desired shape,e.g., arcuate, planar and the like. Pump system 70 may be employed topressurize chamber 54 a appropriately to that end. For example, assumingbending force, B, is greater than force R, pump system 70 would beemployed to evacuate chamber 54 a with sufficient vacuum to counter thebending force B. Were bending force B weaker than force R, pump system70 would be employed to pressurize chamber 54 a appropriately tomaintain planarity of mold 28, or any other desired shape. The exactpressure levels may be determined with a priori knowledge of the forcesR and B which then may be analyzed by a processor (not shown) that maybe included in pump system 70 to pressurize chambers 52 a and 54 a tothe appropriate levels. Also, the forces R and B may be senseddynamically using known techniques so that the pressure within chambers52 a and 54 a may be established dynamically during operation tomaintain substrate 26 with a desired shape. An added benefit is that thepressure in one or both chambers 52 a and 54 a may be established to bea positive pressure, thereby facilitating removal of substrate 26 fromchuck body 42. This also may be accomplished under processor control, ormanually.

Referring again to FIG. 8, when compressing substrate 26 with bladder72, relative movement between substrate 26 and support regions 58 and 60occurs along the X and Y axes. As a result, it is desired that supportregions 58 and 60 have surface regions 58 a and 60 a, respectively,formed thereon from a material adapted to conform to a profile ofsubstrate 26 and resistant to deformation along the x and Y axes. Inthis manner, surface regions 58 a and 60 a resist relative movement ofsubstrate 26 with respect to chuck body 42 in the X and Y directions.

Referring to FIGS. 8 and 13, in another embodiment, chuck body 142 mayinclude one or more walls, or baffles, shown as 142 a, 142 b, 142 c and142 d extending between first and second support regions 158 and 160. Inthis fashion, walls/baffles 142 a, 142 b, 142 c and 142 d segment recess152 into a plurality of sub-regions 152 a, 152 b, 152 c and 152 d thatfunction as sub-chambers once substrate 26 is placed in superimpositiontherewith. Sub-chambers 152 a, 152 b, 152 c and 152 d may be fluid-tightwhich would result in each having a throughway (not shown), placing thesame in fluid communication with pump system 70. Alternatively, or inconjunction therewith sub-chambers 152 a, 152 b, 152 c and 152 d may notform fluid-tight chambers once substrate 26 is placed in superimpositiontherewith. Rather walls 142 a, 142 b, 142 c and 142 d would be spacedapart from substrate 26 to function as a baffle for fluid transferacross the same. As a result, with the appropriate pressure level beingprovided by pump system 70 to recess 152, a pressure differential couldbe provided between sub-chambers 152 a, 152 b, 152 c and 152 d, asdesired.

Referring to both FIGS. 2 and 13, providing walls/baffles 142 a, 142 b,142 c and 142 d with this configuration, sub-regions 152 a, 152 b, 152 cand 152 d may be concurrently provided with differing pressure levels.As a result, the amount of force exerted on substrate 26 when beingpulled-apart from imprinting layer 34 may vary across the surface ofsubstrate 26. This allows cantilevering, or peeling-off of substrate 26from imprinting layer 34 that reduces distortions or defects from beingformed in imprinting layer 34 during separation of substrate 26therefrom. For example, sub-chamber 152 b may have a pressureestablished therein that is greater than the pressure associated withthe remaining sub-chambers 152 a, 152 c and 152 d. As a result, whenincreasing distance “d”, the pulling force of the portion of substrate26 in superimposition with sub-chambers 152 a, 152 c and 152 d issubjected to is greater than the pulling force to which the portion ofsubstrate 26 in superimposition with sub-chamber 152 b is subjected.Thus, the rate that “d” increases for the portion of substrate 26 insuperimposition with sub-chambers 152 a, 152 c and 152 d is acceleratedcompared to the rate at which “d” increases for the portion of substrate26 in superimposition with sub-chamber 152 b, providing theaforementioned cantilevering effect.

In yet another embodiment, shown in FIG. 14, chuck body 242 includes aplurality of pins 242 a projecting from a nadir surface 252 a of outrecess 252. Pins 242 a provide mechanical support for the substrate (notshown) retained on chuck body 242 via vacuum. This enables supportregions 258 and 260 to have surface regions 258 a and 260 a,respectively, formed from material that is fully compliant with thesurface (not shown) of the substrate (not shown) resting against supportregions 258 and 260. In this manner, surface regions 258 a and 260 aprovide a fluid-tight seal with the substrate (not shown) in thepresence of extreme surface variation, e.g., when particulate matter ispresent between the surface (not shown) of the substrate (not shown) andthe surface regions 258 a and 260 a. Mechanical support of the substrate(not shown) in the Z-direction need not be provided by surface regions258 a and 260 a. Pins 242 a provide this support. To that end, pins 242a are typically rigid posts having a circular cross-section.

Referring to FIGS. 11, 12 and 15, in operation, an accurate measurementof wafer 30 in an X-Y plane is undertaken at step 200. This may beachieved by sensing gross alignment fiducials 110 b present on wafer 30using machine vision devices (not shown) and known signal processingtechniques. At step 202, the temperature of wafer 30 may be varied,i.e., raised or lowered, so that the area of one of regions a-l isslightly less than an area of the original pattern on mold 28. Thetemperature variations may be achieved using a temperature controlledchuck or pedestal (not shown) against which wafer 30 rests. The area ofeach of regions a-l can be determined by measurement of a change indistance between two collinear gross alignment fiducials 110 b.

Specifically, a change in the distance between two gross alignmentfiducials 110 b collinear along one of the X- or Y-axes is determined.Thereafter, this change in distance is divided by a number of adjacentregions a-l on the wafer 30 along the X-axis. This provides thedimensional change of the areas of regions a-l attributable todimensional changes in wafer 30 along the X-axis. If necessary, the samemeasurement may be made to determine the change in area of regions a-ldue to dimensional changes of wafer 30 along the Y-axis. However, it mayalso be assumed that the dimensional changes in wafer 30 may be uniformin the two orthogonal axes, X and Y.

At step 204, compressive forces, F₁ and F₂, are applied to mold 28 toestablish the area of the original pattern to be coextensive with thearea of one of the regions a-l in superimposition with the pattern. Thismay be achieved in real-time employing machine vision devices (notshown) and known signal processing techniques to determine when two ormore of alignment marks 114 a are aligned with two or more of fiducialmarks 110 a. At step 206, after proper alignment is achieved andmagnification/run-out errors are reduced, if not vitiated, the originalpattern is recorded in the region a-l that is in superimposition withmold 28, forming the recorded pattern. It is not necessary thatcompression forces F₁ and F₂ have the same magnitude as the dimensionalvariations in either wafer 30 or mold 28 may not be uniform in alldirections. Further, the magnification/run-out errors may not beidentical in both X-Y directions. As a result, compression forces F₁ andF₂ may differ to compensate for these anomalies. Furthermore, to ensuregreater reduction in magnification/run-out errors, the dimensionalvariation in mold 28 may be undertaken after mold 28 contacts imprintinglayer 124, shown in FIG. 6. However, this is not necessary.

Referring again to FIGS. 6, 11 and 12, the alignment of mold 28 withregions a-l in superimposition therewith may occur with mold 28 beingspaced-apart from imprinting layer 124. Were it found that themagnification/run-out errors were constant over the entire wafer 30,then the magnitude of forces F₁ and F₂ could be maintained for eachregion a-l in which the original pattern is recorded. However, were itdetermined that the magnification/run-out errors differed for one ormore regions a-l, steps 202 and 204, shown in FIG. 15, would then beundertaken for each region a-l in which the original pattern isrecorded. It should be noted that there are limits to the relativedimensional changes that may occur between wafer 30 and mold 28. Forexample, the area of the regions a-l should be of appropriate dimensionsto enable pattern on mold 28 to define an area coextensive therewithwhen mold 28 is subject to compression forces F₁ and F₂, withoutcompromising the structural integrity of mold 28.

Referring to FIGS. 5 and 16, in accordance with another embodiment ofthe present invention, accurate measurement of wafer 30 in an X-Y planeis undertaken at step 300. At step 302, the dimensions of one of regionsa-l in superimposition with mold 28 is determined. At step 304 it isdetermined whether the area of one of regions a-l in superimpositionwith mold 28 is larger than the area of the pattern on mold 28. If thisis the case, the process proceeds to step 306, otherwise the processproceeds to step 308. At step 308, mold 28 is placed in contact with theregion a-l in superimposition therewith, and the requisite magnitude ofcompressive forces F₁ and F₂ is determined to apply to mold 28 to ensurethat the area of the pattern is coextensive with the area of this regiona-l. At step 310, compressive forces F₁ and F₂ are applied to mold 28.Thereafter, mold 28 is spaced-apart from the region a-l insuperimposition with mold 28 and the process proceeds to step 312 whereit is determined whether there remain any regions a-l on wafer 30 inwhich to record the original pattern. If there are, the process proceedsto step 314 wherein mold 28 is placed in superimposition with the nextregion and the process proceeds to step 304. Otherwise, the process endsat step 316.

Were it determined at step 304 that the region a-l in superimpositionwith mold 28 had an area greater than the area of the pattern, then theprocess proceeds to step 306 wherein the temperature of mold 28 isvaried to cause expansion of the same. In the present embodiment, mold28 is heated at step 306 so that the pattern is slightly larger than thearea of region a-l in superimposition therewith. Then the processcontinues at step 310.

The embodiments of the present invention described above are exemplary.Many changes and modifications may be made to the disclosure recitedabove, while remaining within the scope of the invention. For example,by pressurizing all chambers formed by the chuck body-substratecombination with positive fluid pressure, the substrate may be quicklyreleased from the chuck body. Further, many of the embodiments discussedabove may be implemented in existing imprint lithography processes thatdo not employ formation of an imprinting layer by deposition of beads ofpolymerizable material. Exemplary processes in which differingembodiments of the present invention may be employed include a hotembossing process disclosed in U.S. Pat. No. 5,772,905, which isincorporated by reference in its entirety herein. Additionally, many ofthe embodiments of the present invention may be employed using a laserassisted direct imprinting (LADI) process of the type described by Chouet al. in Ultrafast and Direct Imprint of Nanostructures in Silicon,Nature, Col. 417, pp. 835–837, June 2002. Therefore, the scope of theinvention should be determined not with reference to the abovedescription, but instead should be determined with reference to theappended claims along with their full scope of equivalents.

1. A chucking system to hold a substrate, said chucking systemcomprising: a chuck body having a side with a pair of spaced-apartsupport regions extending therefrom terminating in a plane, said pair ofspaced-apart support regions having a recess defined therebetween, witha portion of said chuck body in superimposition with said recess beingtransparent to radiation having a predetermined wavelength, with saidchuck body being defined between said side and said plane.
 2. Thechucking system as recited in claim 1 wherein said radiation includesradiation having ultra-violet wavelengths.
 3. The chucking system asrecited in claim 1 wherein said chuck body further includes anadditional support region spaced-apart from one of said pair ofspaced-apart support regions, with an additional recess disposedtherebetween.
 4. The chucking system as recited in claim 3 wherein saidadditional recess includes a plurality of spaced-apart pins extendingtherefrom.
 5. The chucking system as recited in claim 1 wherein saidpair of spaced-apart support regions has a support surface associatedtherewith, facing away from said side, with said support surface beingformed from a material adapted to conform to a profile of saidsubstrate.
 6. The chucking system as recited in claim 3 wherein each ofsaid plurality of support regions has a support surface associatedtherewith, facing away from said side, with said support surface beingformed from a material compliant in a first direction extending betweensaid side and said plane to conform to a profile of said substrate whilebeing resistant to movement in a direction transverse to said firstdirection.
 7. The chucking system as recited in claim 3 furtherincluding a wall disposed within said additional recess, extendingbetween one of said spaced-apart support regions and said additionalsupport region to segment said additional recess into a plurality ofsub-chambers.
 8. The chucking system as recited in claim 3 wherein saidsupport regions have a shape that is selected from a set of shapesconsisting of annular, polygonal and circular.
 9. The chucking system asrecited in claim 3 wherein said chuck body further includes an exteriorsurface and a throughway extending through said chuck body placing saidrecesses in fluid communication with said exterior surface.
 10. Thechucking system as recited in claim 9 further including a pressurecontrol system in fluid communication with said throughway, with saidsubstrate resting against said support region, covering said recess,defining a chamber, with said pressure control system operating tocontrol a pressure in said chamber.
 11. A chucking system to hold asubstrate, said chucking system comprising: a chuck body having a sidewith a pair of spaced-apart support regions extending therefromterminating in a plane, said pair of spaced-apart support regions havinga recess defined therebetween, with a portion of said chuck body insuperimposition with said recess being transparent to ultra-violetradiation, with said pair of spaced-apart support regions having asupport surface associated therewith, facing away from said side, withsaid support surface being formed from a material compliant in a firstdirection extending between said side and said plane to conform to aprofile of said substrate while being resistant to movement in adirection transverse to said first direction, with said chuck body beingdefined between said side and said plane.
 12. The chucking system asrecited in claim 11 wherein said chuck body further includes anadditional support region spaced-apart from one of said pair ofspaced-apart support regions, with an additional recess disposedtherebetween.
 13. The chucking system as recited in claim 12 whereinsaid additional recess includes a plurality of spaced-apart pinsextending therefrom.
 14. The chucking system as recited in claim 13further including a wall disposed within said additional recess,extending between one of said support regions and said additionalsupport region to segment said additional recess into a plurality ofsub-chambers.
 15. The chucking system as recited in claim 14 whereinsaid support regions have a shape that is selected from a set of shapesconsisting of annular, polygonal and circular.
 16. The chucking systemas recited in claim 12 wherein said chuck body further includes anexterior surface and a throughway extending through said chuck bodyplacing said recesses in fluid communication with said exterior surfaceand a pressure control system in fluid communication with saidthroughway, with said substrate resting against said support region,covering said recess, defining a chamber, with said pressure controlsystem operating to control a pressure in said chamber.
 17. A chuckingsystem to hold a substrate, said chucking system comprising: a chuckbody having first and second opposed sides, with said body includingsub-portions extending from said second side terminating in a plane anddefining a recess therebetween, with remaining portions of said bodybeing disposed between said plane and said first side, with a portion ofsaid body in superimposition with said recess being transparent toradiation having a predetermined wavelength.
 18. The chucking system asrecited in claim 17 wherein said first side further includes anadditional sub-portion spaced-apart from one of said sub-portions, withan additional recess disposed therebetween.
 19. The chucking system asrecited in claim 18 wherein said additional recess includes a pluralityof spaced-apart pins extending therefrom.
 20. The chucking system asrecited in claim 19 further including a wall disposed within saidadditional recess, extending between one of said sub-portions and saidadditional sub-portion to segment said additional recess into aplurality of sub-chambers.